With a one‐dimensional particle‐in‐cell simulation model, we have investigated the gap formation around 0.5 of the quasi‐parallel whistler‐mode waves excited by an electron temperature anisotropy. When the frequencies of excited waves in the linear stage cross 0.5, or when they are slightly larger than 0.5 but then drift to lower values, the Landau resonance can make the electron distribution form a beam‐like/plateau population. Such an electron distribution only slightly changes the dispersion relation of whistler‐mode waves, but can cause severe damping around 0.5 via cyclotron resonance. At last, the wave spectrum is separated into two bands with a power gap around 0.5. The condition under different electron temperature anisotropy and plasma beta is also surveyed for such kind of power gap. Besides, when only the waves with frequencies lower than 0.5 are excited in the linear stage, a power gap can also be formed due to the wave‐wave interactions, i.e., lower band cascade. Our study provides a clue to reveal the well‐known 0.5 power gap of whistler‐mode waves ubiquitously observed in the inner magnetosphere.

中文翻译：

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电子温度各向异性激发的惠斯勒波在0.5Ωe附近的间隙形成

利用一维粒子内模拟模型，我们研究了由电子温度各向异性激发的准平行的惠斯勒模式波的0.5附近的间隙形成。当线性级中的激发波频率超过0.5时，或者当它们稍大于0.5但随后漂移到较低值时，朗道共振可使电子分布形成束状/高原态。这样的电子分布只会稍微改变惠斯勒波的色散关系，但是会通过回旋加速器共振而在0.5左右产生严重的阻尼。最后，将波谱分为两个频带，功率间隙约为0.5。对于这种功率间隙，还研究了在不同电子温度各向异性和等离子体β下的条件。此外，当只有线性频率下的频率低于0.5的波被激发时，由于波与波的相互作用，即较低的频带级联，也会形成功率间隙。我们的研究提供了线索，揭示了在内部磁层普遍观察到的惠斯勒模式波的0.5功率间隙。